Preparation of hydroxycarboxylic acids and derivatives thereof



United States Patent 3,405,174 PREPARATION OF HYDROXYCARBOXYLIC ACIDSAND DERIVATIVES THEREOF Gerald Sugerman, Fort Lee, and John Kollar,Wallington,

N.J.,'assignorsto Halcon International, Inc., a corporation of DelawareNo Drawing. Continuation-impart of application Ser. N 0. 273,544, Apr.17, 1963. This application Nov. 17, 1965, Ser. No. 508,392

Claims. (Cl. 260-535) ABSTRACT OF THE DISCLOSURE A cycloalkanol oxidateis rearranged to a hydroxy carboxylic acid and/or derivatives thereof bycontacting with an organic acid having at least 2 carbon atoms and a pKbelow about 4.8.

preparation of caprolactam, a valuable starting material for 'nylon 6,and caprolactone. By further oxidation, adipic acid also may be producedfrom these derivatives.

Prior techniques for the preparation of hydroxycarboxylic acids andderivatives thereof, for example, omegahydroxycaproic acid andomega-hydroxyvaleric acid, utilized mineral acids as the rearrangingacids. The use of these materials, however, has disadvantages which haveretarded the development of a successfully commercial process. Forexample, the mineral acids such as hydrofluoric acid, in order to beefiective, must be introduced into the rearrangement in a substantiallyanhydrous form. Since the hydrofluoric acid must be recycled in acommercial process, and further since water is formed in therearrangement, it is necessary to separate this water from the hydrogenfluoride. This is particularly diflicult because hydrofluoric acid formsan azeotrope with water which is extremelyjdifificult to separate.

In accordance with this invention, it has been found that cycloalkanoloxidates may be rearranged to hydroxycarboxylic acids and derivativesthereof by using a strong organic carboxylic acid as the rearrangingagent. The derivatives of the hydroxycarboxylic acid include oligomersor polymers of the hydroxycarboxylic acid, or esters of thehydroxycarboxylic acid.

The cycloalkanols, the oxidates of which are treated herein, may bedefined by the general formula:

wherein n is a whole integer from 4 to 11 and each R is selected fromthe group consisting of hydrogen; an alkyl group having from 1 to 16carbon atoms preferably from 1 to 6; an aryl group having from 6 to 14carbon atoms; an aralkyl group having from 7 to 16 carbon atoms; aheteroaromatic group; a carboxylic group; a fluoro group; and a chlorogroup. Examples of these compounds include cyclopentanol; cyclohexanol;cycloheptanol; cyclooctanol; cyclodecanol; and cyclododecanol.Substituted alkyl compounds include Z-methylcyclohexanol;2,3-dimethylcyclooctanol; 2,3-dimethyl-4-ethylcyclododecanol; and2-isopropylcyclopentanol. Other compounds include Z-benzylcyclohexanol;2-(3-methylbenzyl-)cyclohexanol; Z-(pyridyl-)cyclopentanol;3-carbomethoxycycloheptanol; 4-carbethoxycyclohexanol; and2,3,4,5,-tetrafluorocyclo hexanol. I

The hydroxycarboxyl acids are generally of the omega type, i.e., havingthe hydroxyl radical on the carbon atoms at the end of the chainopposite the carboxyl group. However, in the case where a carbon atom ofa carbon containing radical is bonded to the ortho position in respectto the peroxide group, acids in addition to the omega type are formed.More generally, it may be stated that (n+1)-hydroxycaproic acids areformed, wherein (n+1) represents the number of carbons in the ring ofthe cycloalkanol precursor, as n was previously defined. As an exampleof products formed, the oxidation and rearrangement ofZ-methylcyclohexanol may be considered. The major product obtained fromthe rearrangement of the oxidate would be 6-hydroxheptanoic acid.

The cycloalkanol oxidate may be obtained in various known ways. Forexample, it may be obtained by the reaction of molecular oxygen with acycloalkanol or by the reaction of cycloalkanone with hydrogen peroxide.It is preferable to oxidize from 10 to 30% of the cycloalkanol. Theoxidation may be initiated by a peroxide and accomplished by passingmolecular oxygen, pure or diluted with an inert gas, such as nitrogen,through the cycloalkanol with good agitation at temperatures of fromabout 60 to about 140 C. The pressures may be from atmospheric to 1000p.s.i.a. or higher. The oxidate consists of a solution in thecycloalkanol of peroxide compounds along with minor amounts of acid,esters and ketones. Generally, the oxidate" contains from 0.4 to 3millimoles of peroxidic oxygen per gram of oxidate. A discussion of theproducts present in such an oxidate is found in an article by Brown et-al., J.A.C.S., 77, pp. 1756-1759.

Furthermore concentration of the oxidate by distillation, preferablyunder vacuum, can be achieved so as to obtain peroxide concentrations ofup to about 0.5 mole of peroxide/ grams. Such concentrates are alsosuitable.

The cycloalkanol oxidate, thus constituted, is treated in accordancewith the present invention with an organic acid having a dissociationconstant less than 4.8 at reaction temperatures between 0 and 200 C.,preferably from 25 to C., and most desirably between 40 and 95 C. Thepressure, while not of particular significance, should preferably beapproximately atmospheric. When higher temperatures are employed, suchas in excess of about 80 C., superatmospheric pressures are convenientto minimize the evaporation of the organic acids, and the otherconstituents present. The organic acid treatment results in a conversionof the peroxide compounds in the cycloalkanol oxidate to yieldhydroxycarboxylic acids, oligomers or polymers of the hydroxycarboxylicacid, or esters of the hydrocarboxylic acid.

The strong organic carboxylic acids used in the instant invention have apK (dissociation constant) of less than 4.8, preferably. below 4.2, andmost desirably below 3.8. Examples of such acids include acetic acid,adipic acid, benzoic acid, fumaric acid, maleic acid, oxalic acid,phthalic acid, trifluoroacetic acid and toluic acid. Where available, ofcourse, the anhydride may be added, if Water is present, in lieu of theacid. The above enumeration is not intended to be complete. For aplentary listing see Hodgman et al., Handbook of Chemistry & Physics,The Chemical Rubber Publishing Co., Cleveland (1960), volume 42, pp.1753-1756.

The amount of the strong organic carboxylic acid should be at least 0.2mole per mole of peroxidic and hydroxyl groups. Generally, more than 2moles per mole would be the practical upper limit, however, greateramounts may be added without detriment to the rearrangement. Preferably,0.5 to 1.5 moles per total moles of hydroxyl and peroxide group, andmost desirably, 0.9 to 1.2 moles per total mole of said components areused.

In a particularly preferred embodiment of the instant invention, acorresponding ketone is added to increase the yield. For example, when acyclohexanol oxidate is being rearranged, cyclohexanone may be added.These corresponding ketones can be characterized by the general formula:

oat REE).

LJ where R, and n, are as defined previously. Generally, between 1 andmoles of the ketone per mole of peroxide oxygen, preferably, between 1and 3 moles per mole, are employed. Amounts of the ketone exceeding 5moles per mole may be used, but generally no advantage results and it iseconomically undesirable.

The hydroxycarboxylic acids and derivatives thereof may be readilyconverted in known manner to lactams and lactones. For example, byheating the hydroxycaproic acid to about 295 C. for about hours in anautoclave at a pressure of 2000 to 2500 p.s.i.g., in the presence ofammonia and water, caprolactam may be prepared.

In order to more fully illustrate the invention, attention is directedtowards the following example:

EXAMPLE Cyclohexanol oxidate is prepared by mixing 700 parts ofcyclohexanol, 7 grams of commercial cyclohexanone peroxide and 7 gramsof powdered calcium carbonate in a flask. Oxygen is bubbled through themixture at a rate of 0.7 liter per minute (N.T.P.) while the temperatureis rapidly raised to 120 C. After 8 liters of oxygen are absorbed, theflask is cooled to 110 C. and the oxygen passed therethrough until atotal of 17 liters of oxygen are absorbed. Titration of the oxidateindicates the presence of approximately 0.1 mole of peroxidic oxygen pergrams of the oxidate. After filtering the oxidate free 5 shows theeffect of the addition of various strong organic 5 acids on therearrangement.

It will be noted that the yield is markedly improved in each and everycase. While the thermal decomposition gives yields of only about 3%, asshown in run No. 1, even the least effective acid cited, namely, aceticacid, more than triples theyield. Yields up to 39% are obtained by theaddition of other acids.

It will be understood that modifications and variations may be effectedwithout departing from the spirit of the invention.

What is claimed is:

1. A process for the preparation of hydroxycarboxylic acids andderivatives thereof which comprises contacting an oxidate of a cyclicsecondary alcohol having from 4 to 12 ring carbon atoms at temperaturesbetween 0 C. and 100 C. with at least 0.2 mol of an organic carboxylicacid selected from the group'consisting of acetic acid, adipic acid,benzoic acid, fumaric acid, maleic acid, oxalic acid, phthalic acid,trifluoro acetic acid and toluic acid per mol of peroxidic and hydroxygroups in said oxidate.

2. A process according to claim 1 wherein the cyclic secondary alcoholis cyclohexanol.

3. A process according to claim 1 wherein the rearrangement is performedin the presence of a ketone which corresponds to the cyclic secondaryalcohol.

4. A process according to claim 1 wherein cyclic secondary alcohol iscontacted with oxygen to form an oxidate of the cyclic secondaryalcohol.

5. A process according to claim 4 wherein the cyclic secondary alcoholis cyclohexanol and wherein said cyclohexanol is contacted withmolecular oxygen at a temperature between about 60 C. and about C.

References Cited UNITED STATES PATENTS OTHER REFERENCES Brown et al.,J.A.C.S., v01. 77, pp. 1756-1759.

LORRAINE A. WEINBERGER, Primary Examiner.

A. P. HALLUIN, Assistant Examiner.

